1. Field of the Invention
The present invention relates to an electric actuator which makes it possible to transport, for example, a workpiece in accordance with a displacement action of a movable member.
2. Description of the Related Art
The electric actuator has been hitherto used to transport, for example, a workpiece. Such an electric actuator concerning the conventional technique is shown in FIG. 7.
The electric actuator 1 comprises an opening extending in the longitudinal direction corresponding to its upper surface, and it further comprises lengthy outer rails 3 having a pair of mutually opposing rolling surfaces 2a, 2b formed on inner wall surfaces. A ball screw shaft 4 for transmitting the rotary driving force of an unillustrated motor is arranged in the opening formed by the outer rails 3. The ball screw shaft 4 is rotatably supported at its both ends by the aid of a support plate 5 and a motor bracket 6.
An inner block 7 for converting the rotary motion of the ball screw shaft 4 into the rectilinear motion in accordance with the engaging action of the ball screw shaft 4 is provided in the opening formed by the outer rails 3. The inner block 7 makes reciprocating movement along the longitudinal direction of the outer rails 3 in accordance with the rotary action of the ball screw shaft 4.
Circulating tracks 9 for circulating a plurality of balls 8 in accordance with the rolling action on the rolling surfaces 2a, 2b are formed on the inner block 7. In this case, the plurality of balls 8 function to smoothly guide the inner block 7 along the opening formed by the outer rails 3.
However, in the case of the electric actuator 1 concerning the conventional technique, the inner block 7 functions as a movable member to which an unillustrated slide table is installed for placing a workpiece thereon. Further, the inner block 7 also functions as a nut member to be fitted to the ball screw shaft 4. Furthermore, the inner block 7 also functions as a guide block through which the plurality of balls 8 roll and circulate therethrough. That is, the inner block 7 is formed by a block member which is formed in an integrated manner and which is provided with all of the foregoing functions.
Therefore, the electric actuator 1 concerning the conventional technique involves the following inconvenience. That is, for example, if the inner block 7 is damaged or worn, the entire inner block 7 including the plurality of balls 8 must be exchanged with a new inner block 7. Therefore, the maintenance cost is increased.
A general object of the present invention is to provide an electric actuator which makes it possible to reduce the maintenance cost by detachably providing a movable mechanism and a guide mechanism separately from each other.
A principal object of the present invention is to provide an electric actuator which is preferably usable in an environment such as a clean room in which cleanliness is required.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.